Yesterday, Maria Caulfield and Ben Bradley also announced they were quitting as vice-chairs of the Conservative Party.

After the general election the DUP secured a promise of £1bn from the Conservatives in a 'confidence and supply' agreement that would see their 10 MPs lend their support to the Tories on key Westminster votes.

Jon Tonge, Professor of Politics at Liverpool University, said that despite the noise from some commentators, the chances of a successful leadership challenge or another general election were slim.

"I don't think it will affect the confidence and supply agreement," he said.

"The Government have nowhere to go, other than down DUP lane.

"They're friendless otherwise at Westminster. If there was a contest and Theresa May was to step down, her successor would still have to cling to Nigel Dodds whether that marriage be loveless or otherwise."

Mr Tonge said the DUP had so far been "pretty unfailing" in its support of the Government as long as Northern Ireland was treated the same as the rest of the United Kingdom.

"The only way the DUP would pull support from the Government would be if Northern Ireland was to be treated as a place apart in any negotiations. I don't see the Conservatives risking that," he added.

"Whoever a successor would be, and I'm not sure there's enough unity in the assassins to get rid of Theresa May, the need for the DUP remains pretty strong."

He said the risk of a general election was even lower as the Conservatives lost their majority last year and ended up deeply in debt to the DUP.

Only 48 MPs are needed to force a leadership contest within the Conservative Party, but Professor Tonge said they don't have the numbers to go the distance.

"Would Theresa May feel her authority was undermined by the fact that 48 of her own MPs moved against her? Would she fall on her sword or tough it out? I think the latter option is more than likely on the grounds she could win," he said.

"It could be a fatal mistake for the Brexiteers, as it would mean Theresa May's authority is reinforced.

"So far, I think Theresa May's position isn't as precarious as some commentators suggest."

In the unlikely event of a fresh election, Professor Tonge said the DUP could kiss goodbye to the £1bn if a Jeremy Corbyn-led Labour Government got into power.

"If the DUP was still kingmaker they could maybe secure even better terms with the Conservatives," he said.

"I certainly wouldn't see a Corbyn-led Government honouring anything to the DUP. I think they could forget about the £1bn minus what has already been paid.

"The DUP couldn't look to a Corbyn Government for any favours.

"Also, the DUP aren't really going to lose any seats. The only person who would be seriously worried would be Lady Sylvia Hermon in North Down - so it could be 11 DUP MPs."